Military vehicles must be functional in the rain, and some are amphibious. Accumulations of water must be drained, but drains must keep out water when the vehicle swims.
Applicant and patent counsel know of no prior art pertinent to the claimed invention of this application. Drain and check valves of the known prior art are subject to clogging. Military vehicles should provide for automatic draining of water by means of a check valve which will not clog and which will not admit water when the vehicle must swim.